Re: [PATCH v2 3/3] tpm: retrieve digest size of unknown algorithms with PCR read
From: Roberto Sassu
Date: Mon Sep 17 2018 - 06:03:03 EST
On 9/16/2018 2:37 PM, Jarkko Sakkinen wrote:
On Wed, Sep 05, 2018 at 01:42:02PM +0200, Roberto Sassu wrote:
Currently, the TPM driver retrieves the digest size from a table mapping
TPM algorithms identifiers to identifiers defined by the crypto subsystem.
If the algorithm is not defined by the latter, the digest size can be
retrieved from the output of the PCR read command.
The patch retrieves at TPM startup the digest sizes for each PCR bank and
stores them in the new structure tpm_active_bank_info, member of tpm_chip,
so that the information can be passed to other kernel subsystems.
tpm_active_bank_info contains: the TPM algorithm identifier, necessary to
generate the event log as defined by Trusted Computing Group (TCG); the
digest size, to pad/truncate a digest calculated with a different
algorithm; the crypto subsystem identifier, to calculate the digest of
event data.
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
drivers/char/tpm/tpm-interface.c | 11 +++++++---
drivers/char/tpm/tpm.h | 4 ++--
drivers/char/tpm/tpm2-cmd.c | 47 ++++++++++++++++++++++++++++++----------
include/linux/tpm.h | 6 +++++
4 files changed, 51 insertions(+), 17 deletions(-)
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 81872880b5f1..02dcdcda5a3c 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -993,7 +993,7 @@ int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
if (!chip)
return -ENODEV;
if (chip->flags & TPM_CHIP_FLAG_TPM2)
- rc = tpm2_pcr_read(chip, pcr_idx, count, digests);
+ rc = tpm2_pcr_read(chip, pcr_idx, count, digests, NULL);
else
rc = tpm_pcr_read_dev(chip, pcr_idx, digests[0].digest);
tpm_put_ops(chip);
@@ -1056,8 +1056,8 @@ int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
memset(digest_list, 0, sizeof(digest_list));
for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
- chip->active_banks[i] != TPM_ALG_ERROR; i++) {
- digest_list[i].alg_id = chip->active_banks[i];
+ chip->active_banks[i].alg_id != TPM_ALG_ERROR; i++) {
+ digest_list[i].alg_id = chip->active_banks[i].alg_id;
Why not just zero?
Hi Jarkko
sorry, I didn't understand this comment. Did you refer to the code
below (chip->active_banks[0] ...)?
memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
count++;
}
@@ -1158,6 +1158,11 @@ int tpm1_auto_startup(struct tpm_chip *chip)
goto out;
}
+ chip->active_banks[0].alg_id = TPM_ALG_SHA1;
+ chip->active_banks[0].digest_size = hash_digest_size[HASH_ALGO_SHA1];
+ chip->active_banks[0].crypto_id = HASH_ALGO_SHA1;
+ chip->active_banks[1].alg_id = TPM_ALG_ERROR;
Then you could drop the last line here.
This code has the same behavior of tpm2_get_pcr_allocation(). If some
banks are not used, set the algorithm of the first unused to
TPM_ALG_ERROR.
+
return rc;
out:
if (rc > 0)
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 9479e1ae1b4c..385843b49c17 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -237,7 +237,7 @@ struct tpm_chip {
const struct attribute_group *groups[3];
unsigned int groups_cnt;
- u16 active_banks[7];
+ struct tpm_active_bank_info active_banks[7];
#ifdef CONFIG_ACPI
acpi_handle acpi_dev_handle;
char ppi_version[TPM_PPI_VERSION_LEN + 1];
@@ -565,7 +565,7 @@ static inline u32 tpm2_rc_value(u32 rc)
}
int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
- struct tpm_digest *digests);
+ struct tpm_digest *digests, u16 *sizes);
int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
struct tpm_digest *digests);
int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 601d67c76c1e..51d2454c5329 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -181,11 +181,12 @@ struct tpm2_pcr_read_out {
* @pcr_idx: index of the PCR to read.
* @count: number of digests passed.
* @digests: list of pcr banks and buffers current PCR values are written to.
+ * @sizes: list of digest sizes.
*
* Return: Same as with tpm_transmit_cmd.
*/
int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
- struct tpm_digest *digests)
+ struct tpm_digest *digests, u16 *sizes)
{
int rc;
struct tpm_buf buf;
@@ -215,6 +216,9 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
memcpy(digests[0].digest, out->digest,
be16_to_cpu(out->digest_size));
+
+ if (sizes)
+ sizes[0] = be16_to_cpu(out->digest_size);
}
tpm_buf_destroy(&buf);
@@ -245,7 +249,6 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
struct tpm2_null_auth_area auth_area;
int rc;
int i;
- int j;
if (count > ARRAY_SIZE(chip->active_banks))
return -EINVAL;
@@ -267,14 +270,9 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
tpm_buf_append_u32(&buf, count);
for (i = 0; i < count; i++) {
- for (j = 0; j < ARRAY_SIZE(tpm2_hash_map); j++) {
- if (digests[i].alg_id != tpm2_hash_map[j].tpm_id)
- continue;
- tpm_buf_append_u16(&buf, digests[i].alg_id);
- tpm_buf_append(&buf, (const unsigned char
- *)&digests[i].digest,
- hash_digest_size[tpm2_hash_map[j].crypto_id]);
- }
+ tpm_buf_append_u16(&buf, digests[i].alg_id);
+ tpm_buf_append(&buf, (const unsigned char *)&digests[i].digest,
+ chip->active_banks[i].digest_size);
}
rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0,
@@ -851,6 +849,26 @@ int tpm2_probe(struct tpm_chip *chip)
}
EXPORT_SYMBOL_GPL(tpm2_probe);
+static int tpm2_init_active_bank_info(struct tpm_chip *chip,
+ struct tpm_active_bank_info *active_bank)
+{
+ struct tpm_digest digest = {.alg_id = active_bank->alg_id};
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
+ enum hash_algo crypto_algo = tpm2_hash_map[i].crypto_id;
+
+ if (active_bank->alg_id != tpm2_hash_map[i].tpm_id)
+ continue;
+
+ active_bank->digest_size = hash_digest_size[crypto_algo];
+ active_bank->crypto_id = crypto_algo;
+ return 0;
+ }
+
+ return tpm2_pcr_read(chip, 0, 1, &digest, &active_bank->digest_size);
+}
+
struct tpm2_pcr_selection {
__be16 hash_alg;
u8 size_of_select;
@@ -905,7 +923,12 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
}
memcpy(&pcr_selection, marker, sizeof(pcr_selection));
- chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
+ chip->active_banks[i].alg_id =
+ be16_to_cpu(pcr_selection.hash_alg);
+ rc = tpm2_init_active_bank_info(chip, &chip->active_banks[i]);
+ if (rc)
+ break;
+
sizeof_pcr_selection = sizeof(pcr_selection.hash_alg) +
sizeof(pcr_selection.size_of_select) +
pcr_selection.size_of_select;
@@ -914,7 +937,7 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
out:
if (i < ARRAY_SIZE(chip->active_banks))
- chip->active_banks[i] = TPM_ALG_ERROR;
+ chip->active_banks[i].alg_id = TPM_ALG_ERROR;
tpm_buf_destroy(&buf);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index ac9fc47f4494..c8372ff582c3 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -46,6 +46,12 @@ struct tpm_digest {
u8 digest[SHA512_DIGEST_SIZE];
} __packed;
+struct tpm_active_bank_info {
+ u16 alg_id;
+ u16 digest_size;
+ u16 crypto_id;
+};
Why not just tpm_bank_info? Will there be also tpm_inactive_bank_info
at some point?
It derived from chip->active_banks. I will rename the structure.
Thanks
Roberto